A method for luminance transition improvement includes the following steps: inputting an image comprising a plurality of pixels comprising a first pixel; generating an extreme gray level according to the plurality of pixels; generating a first gray level difference according to the gray level of the first pixel and the extreme gray level; generating a first gray level adjustment value according to the first gray level difference, a first weighted value, a second weighted value, and a first order differential value of the gray level of the first pixel relative to a spatial coordinate; and generating an adjusted gray level of the first pixel according to the first gray level adjustment value and the gray level of the first pixel.
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1. A method for luminance transition improvement comprising:
(a) inputting an image comprising a plurality of pixels comprising a first pixel;
(b) generating an extreme gray level according to the plurality of pixels;
(c) generating a first gray level difference according to the gray level of the first pixel and the extreme gray level;
(d) generating a first gray level adjustment value according to the first gray level difference, a first weighted value, a second weighted value, and a first order differential value of the gray level of the first pixel relative to a spatial coordinate; and
(e) generating an adjusted gray level of the first pixel according to the first gray level adjustment value and the gray level of the first pixel.
2. The method of
3. The method of
4. The method of
5. The method of
6. The method of
7. The method of
8. The method of
9. The method of
(the sum of gray levels of two pixels neighboring the first pixel at the spatial coordinate)−2*(the gray level of the first pixel). 10. The method of
(the first weighted value)*(the first order differential value of the gray level of the first pixel relative to the spatial coordinate)−(the second weighted value)*(the first gray level difference). 11. The method of
(the absolute value of the difference of gray levels of two pixels neighboring the first pixel at the spatial coordinate)/2. 12. The method of
13. The method of
14. The method of
15. The method of
16. The method of
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1. Field of the Invention
The present invention relates to a method for luminance transition improvement, and more particularly, to a method of adjusting gray levels of pixels within an area having a large gray level variation for luminance transition improvement.
2. Description of the Prior Art
Please refer to
A goal of image processing is to have the features of the boundary area 8 stand out while keeping the image area 6 and the surrounding boundary area 8 in harmony. An adjustment of the image parameters of the whole image 2 will sacrifice some features that are not within the image area 6 or cause distortion of the image area 6. The variation in luminance and spatial range within the boundary area 8 are small, so the blurred edges are obscure especially for the image 2 being enlarged. As the digital display technology progresses, such as digital TV, digital images need to be scaled up when being transferred to digital televisions in large size. There is a need to solve the problem of the blurred edges around the image area 6.
It is therefore a primary objective of the claimed invention to provide a method for luminance transition improvement for solving the above-mentioned problem.
According to claimed invention, a method for luminance transition improvement includes the following steps: inputting an image comprising a plurality of pixels comprising a first pixel; generating an extreme gray level according to the plurality of pixels; generating a first gray level difference according to the gray level of the first pixel and the extreme gray level; generating a first gray level adjustment value according to the first gray level difference, a first weighted value, a second weighted value, and a first order differential value of the gray level of the first pixel relative to a spatial coordinate; and generating an adjusted gray level of the first pixel according to the first gray level adjustment value and the gray level of the first pixel.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Please refer to
Please refer to
Step 100: Input the image 16 with the input device 20. The image 16 includes a plurality of pixels including a first pixel.
Step 102: The processor 18 executes the program 14 to compute the gray level of the first pixel of the image 16, a maximum gray level and a minimum gray level of the first pixel, and gray levels of pixels neighboring the first pixel.
Step 104: The processor 18 executes the program 14 to compute a second order differential value of the gray level of the first pixel relative to the spatial coordinate. When the second order differential value of the gray level of the first pixel relative to the spatial coordinate is not positive, go to Step 106; and when the second order differential value of the gray level of the first pixel relative to the spatial coordinate is positive, go to Step 108.
Step 106: The processor 18 executes the program 14 to compute a first gray level difference. The first gray level difference is the maximum gray level minus the gray level of the first pixel. Go to Step 110.
Step 108: The processor 18 executes the program 14 to compute a first gray level difference. The first gray level difference is the gray level of the first pixel minus the minimum gray level. Go to Step 110.
Step 110: Input a first weighted value and a second weighted value. The processor 18 executes the program 14 to compute a first gray level adjustment value according to the first gray level difference, the first weighted value, the second weighted value, and a first order differential value of the gray level of the first pixel relative to the spatial coordinate. Go to Step 112.
Step 112: The processor 18 executes the program 14. When the second order differential value of the gray level of the first pixel relative to the spatial coordinate is not positive, generate an adjusted gray level of the first pixel by summing the first gray level adjustment value and the gray level of the first pixel. When the second order differential value of the gray level of the first pixel relative to the spatial coordinate is positive, generate the adjusted gray level of the first pixel by subtracting the first gray level adjustment value from the gray level of the first pixel.
The detailed description is introduced as follows. First users can input the image 16 via the input device 20. If the first pixel is processed by the program 14, the pixels neighboring the first pixel will be processed so as to generate extreme gray levels of the first pixel and the pixels neighboring the first pixel. For example, if the left four pixels and right four pixels neighboring the first pixel at the spatial coordinate are considered, the maximum gray level and the minimum gray level of the nine gray levels of the nine pixels are the relative extreme gray levels of the image instead of the absolute extreme gray levels. And then the program 14 is capable of computing the second order differential value of the gray level of the first pixel relative to the spatial coordinate by any numerical methods. For example, the second order differential value of the gray level of the first pixel relative to the spatial coordinate can be (the sum of gray levels of two pixels neighboring the first pixel at the spatial coordinate)−2*(the gray level of the first pixel). Please refer to
(the first gray level adjustment value)=(the first weighted value)*(the first order differential value of the gray level of the first pixel relative to the spatial coordinate)−(the second weighted value)*(the first gray level difference).
The first order differential value of the gray level of the first pixel relative to the spatial coordinate can be computed by any numerical methods. For example, the first order differential value of the gray level of the first pixel relative to the spatial coordinate can be (the absolute value of the difference of gray levels of two pixels neighboring the first pixel at the spatial coordinate)/2. The first weighted value and the second weighted value can be (1,0.25), (2,0.5), (2,0.25), and so on. When the second order differential value of the gray level of the first pixel relative to the spatial coordinate is not positive, the adjusted gray level of the first pixel is generated by summing the first gray level adjustment value and the gray level of the first pixel. When the second order differential value of the gray level of the first pixel relative to the spatial coordinate is positive, the adjusted gray level of the first pixel is generated by subtracting the first gray level adjustment value from the gray level of the first pixel. Any pixel of the image 16 can be processed with the method according to the present invention, especially those pixels having a large variation rate of the gray level to the spatial coordinate, such as the intersectional curve between the first section and the second section as shown in
An overshoot threshold can be provided to limit the range of the adjusted gray level. Please refer to
In contrast to the prior art, the method according to the present invention can adjust the gray level of pixels within an area having a large variation rate of the gray level to the spatial coordinate according to the variation rate of the gray level (the first order differential value of the gray level of the first pixel relative to the spatial coordinate) and the difference between a gray level of a pixel and relative extreme gray levels (the first gray level difference). Furthermore, for preventing the adjusted gray level of the pixel from being too large or too small, an overshoot threshold can be provided to limit the range of the adjusted gray level. The present invention can solve the problem of the blurred edges effectively.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
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